The present invention relates to an exercising machine and, more particularly, to a step exerciser, which uses a coupling device with a horizontal axle bearing block and a vertical axle bearing block to couple each pedal rod to the crank at each end of the wheel axle of a flywheel, so that less noise is produced during the operation of the step exerciser.
FIGS. 1 and 2 show a step exerciser constructed according to the prior art. According to this structure of step exerciser, two cranks 821 are respectively coupled between the ends of the wheel axle of a flywheel 82 and two pedal rods 81, and the pedal rods 81 each have an axle sleeve 812 coupled to a round rod 8211 at one crank 821 and a rear end provided with a roller 811, which is moved with the respective pedal rod 81 in a longitudinal sliding groove 831 of a respective rail 83. This structure of step exerciser has drawbacks. During the operation of the step exerciser, the pedal rods 81 tend to vibrate when moved back and forth along the longitudinal sliding groove 831 of the respective rail 83, resulting in high noise level. Further, a friction resistance is produced in the connection area between each crank 821 and the corresponding pedal rod 81, hindering the movement of the respective pedal rod 81. FIG. 3 illustrates another prior art design, in which the pedal rod 81 has a barrel 912 transversely disposed at its one end and coupled to the round rod 9211 of one crank 921, and a bushing 94 is sleeved onto the round rod 9211 and secured to the inside of the barrel 912 by holding down screws 95. When assembled, a gap 910 is left between the outside wall of the bushing 94 and the inside wall of the barrel 912 to accommodate relative movement between the pedal rod 91 and the crank 921. This design is still not satisfactory in function. Because the holding down screws 95 are directly stopped against the periphery of the bushing 94, the holding down screws 95. wear quickly with use and, much noise is produced during reciprocating motion of the pedal rod 91. Further, because the round rod 912 is coupled to the pedal rod 91 in horizontal direction, driving force is not efficiently transmitted from the pedal rod 91 to the crank 921, and the user must employ much effort to move the pedal rod 91 during the stroke where the crank 921 is moved to vertical position.
The present invention has been accomplished to provide a step exerciser, which eliminates the drawbacks of the aforesaid prior art designs. According to one aspect of the present invention, the step exerciser comprises two pedal rods coupled to two cranks at two sides of the wheel axle of a flywheel for enabling the flywheel to be rotated when the user steps the pedal rods alternatively up and down, and a coupling device is coupled a round rod at one end of each of the cranks and a U-lug at one end of each of the pedal rods, the coupling device having a vertical axle bearing block connected to the U-lug by a screw bolt and a locknut, and a horizontal axle bearing block fixedly connected to the horizontal axle bearing block at right angles and adapted to support the round rod of one of the cranks in the U-lug at one end of one of the pedal rods to reduce friction and noise during operation of the step exerciser. When assembled, a gap is left between the periphery of the horizontal axle bearing block of the coupling device and the inner surface of the U-lug to accommodate the reciprocating motion of the respective pedal rod in the longitudinal sliding groove of the respective rail. According to another aspect of the present invention, the cranks each have a first crank half and a second crank half connected at right angels for transmission of driving force efficiently.